Free volume correlation with electrical conductivity of polycarbonate/reduced graphene oxide nanocomposites studied by positron annihilation lifetime spectroscopy

Abstract

ABSTRACTThe reduced graphene oxide (RGO) was added to polycarbonate (PC) through solvent mixing. The influences of RGO on the free volumes and electrical conductivity of PC were systemically studied by positron annihilation lifetime spectroscopy (PALS), Fourier‐transform infrared spectroscopy, transmission electron microscope, and electrical conductivity measurements for PC/RGO nanocomposites. The nanosized effect, good conductivity of RGO, and strong interfacial interaction between RGO and PC result in the low conductive threshold of 0.36 wt %. Ten orders of magnitude increase in electrical conductivity was obtained. The results of PALS indicate the properties of free volumes fluctuate around the conductive percolation threshold. The conformational change of PC segments in the interfacial region induced by the strong interfacial interaction leads to an increase in free volume radius. The concentration of free volume decreases due to the depression of free volume holes as the introduction of RGO. Significantly, an exponential function is proposed to describe the effect of relative fractional free volume on the electrical conductivity, suggesting that free volume plays an important role in regulating electrical conductivity of PC/RGO. The physical quantity fd that refers required fractional free volume of polymer composites from insulating to conducting phase is found. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48207.